Why File.exists() does not work

问题

I have a file watstheday.txt in my src/main/resources folder of my project as shown in the image file below.

I read the file through a getResourceAsStream() method of the ClassLoader and perform further actions in my code which is working perfectly. However if I try to perform a check if the file exists through the below code it always returns false.

try {
            ClassLoader classLoader = getClass().getClassLoader();
            System.out.println("!@#!@# so difficult to be simple..."+classLoader.getResource("watstheday.txt"));
            //this returns false but the file is there
            System.out.println("@#@ vertigo2 "+new File(classLoader.getResource("watstheday.txt").getFile()).isFile());
            //this ALSO returns false but the file is there
            System.out.println("@#@ vertigo2 "+new File(classLoader.getResource("watstheday.txt").getFile()).exists());
            //Giving the / to mark the root of the application though that's not required
            System.out.println("@#@ vertigo3 "+new File(classLoader.getResource("//watstheday.txt").getFile()).isFile());
            //the below code with getResourceAsStream works absolutely fine and i can read the file
            classLoader.getResourceAsStream("watstheday.txt");
            BufferedReader buf = new BufferedReader(
                    new InputStreamReader(classLoader.getResourceAsStream("watstheday.txt")));
            while (true) {
                lineJustFetched = buf.readLine();
                System.out.println(" @@#@ lineJustFetched =" + lineJustFetched);
            }
            buf.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

I consulted the following posts before finally putting up this Question but couldn’t find what am I doing wrong. When I print the file name it gets printed with the complete deployment path shown as

!@#!@# so difficult to be simple... vfs=$my_server_deployment_folder_location$/helloworld/watstheday.txt

回答1:

Resources are not files. When you develop (say, in an IDE) and haven't packaged the application yet, you may get paths of real files (somewhere in src/main/resources).

However when the application is packaged, resources are entries in an archive. They do not exist as files anymore. So do not use File with resources.

来源：https://stackoverflow.com/questions/48860434/why-file-exists-does-not-work

标签

java

file-io

getresource